I’m not talking about WWII. “Modern tanks” is the key. The gas turbine in the M-1 was a game changer and the Abrams was the first modern tank with a high level of automotive performance described as a cross between a “dump truck and a sports car.” In the early 1970’s, turbo-diesel technology wasn’t quite there yet, and Chrysler (the original producer of U.S. tanks) had significant experience in producing gas turbine engine technology, and in the 1970’s the U.S. Army still had a significant fleet of gas powered vehicles. The U.S. Army and Marine Corp are now indeed thinking seriously of ditching the turbines in favor of an MTU similar to the one in the Leopard II series due to fuel economy issues and the logistical problem of two fuel streams as everything else in now diesel under the hood. They would have done so already if not the Iraq War sapping funds and causing developmental headaches.
AFAIK The T-34 had a massive engine block of two diesel units to give it needed combat power. I’m not sure why diesel units weren’t more popular in WWII AFV’s, but I imagine cost and ease of production and maintenance were issues. Certainly, it was not because the United States or Britain were worried that diesel engines were more combustible than petrol. Diesel burns at much higher pressure and temperature than petrol does, and is certainly a bit safer. But in a tank with large amounts of ammo cooking off, any fuel will eventually burn. Especially with the “Ronson” or “Tommy-Cooker” reputation that the Sherman had, based mainly on ammunition stowage and the lack of wet-stowage, it’s hard to say that diesel powered vehicles are any more vulnerable that gas ones to brewing-up…